There are many instances when it may be desirable to permanently occlude a vessel in the human body. Examples of when permanent occlusion of a vessel might be desirable include: occlusion of an aneurysm or side branch vessel; therapeutic occlusion, or embolization, of the renal artery; occlusion of a Blalock-Taussig Shunt; pulmonary arteriovenous fistulae and transjugular intrahepatic stent shunt occlusion; some non-vascular applications, such as therapeutic ureteric occlusion; and the occlusion of vessels feeding large cancerous tumors.
In the past, certain coiled stents, stent grafts or detachable balloons have been utilized for providing permanent occlusion of vessels. Stent-grafts are essentially endoluminal stents with a discrete covering on either or both of the luminal and abluminal surfaces of the stent that occludes the open spaces, or interstices, between adjacent structural members of the endoluminal stent. It is known in the art to fabricate stent-grafts by covering the stent with endogenous vein or a synthetic material, such as woven polyester known as DACRON, or with expanded polytetrafluoroethylene. Additionally, it is known in the art to cover the stent with a biological material, such as a xenograft or collagen.
There are certain problems associated with coiled stents, including, migration of the coiled stent within the vessel to be occluded, perforation of the vessel by the coiled stent, and failure to completely thrombose, or occlude, the vessel. Another disadvantage associated with such coiled stents is that the vessel may not be immediately occluded following placement in the vessel. Disadvantages associated with detachable occlusion balloons include premature detachment with distal embolization, or occlusion, and they are believed to require a longer period of time for the user of the device to learn how to properly use such detachable occlusion balloons.
In addition to vessel occlusion, conventional graft type intraluminal medical devices are frequently used post-angioplasty in order to provide a structural support for a blood vessel and reduce the incidence of restenosis following percutaneous balloon angioplasty. A principal example are endovascular stents which are introduced to a site of disease or trauma within the body's vasculature from an introductory location remote from the disease or trauma site using an introductory catheter, passed through the vasculature communicating between the remote introductory location and the disease or trauma site, and released from the introductory catheter at the disease or trauma site to maintain patency of the blood vessel at the site of disease or trauma. Stent-grafts are delivered and deployed under similar circumstances and are utilized to maintain patency of an anatomic passageway, for example, by reducing restenosis following angioplasty, or when used to exclude an aneurysm, such as in aortic aneurysm exclusion applications.
While these medical devices have specific advantages, their overall size, in particular the diameter and delivery profile, are significant disadvantages that render these devices prohibitive for certain uses. Another significant disadvantage is the limited flexibility these devices have for navigating paths through small and/or tortuous vessels. As such, they may not be desirable for many small diameter vessel applications, for example neurovascular vessels.
What is needed is a medical device capable of occluding various parts of a vessel that can assume a reduced diameter and delivery profile.